1. Field of the Invention
The present invention relates to an endoscope system and a method for operating an endoscope system.
2. Description Related to the Prior Art
In medical fields, diagnoses using an endoscope system that comprises a light source device for an endoscope (hereinafter simply referred to as the light source device), an endoscope, and a processor device, are widely performed. The light source device generates illumination light to be applied to an object of interest (hereinafter referred to as the object) such as mucosa in a body cavity. The endoscope comprises an image sensor for imaging the object irradiated with the illumination light.
An endoscope system comprising a light source device that emits white light (the illumination light) and a simultaneous-type color sensor (the image sensor) has been known. The color sensor separates the light incident on the endoscope from the object into blue (B) light, green (G) light, and red (R) light and captures them simultaneously.
The light quantities of the B, G, and R light differ from each other in the white light from the light source device depending on the properties of the light sources, and the spectral sensitivity (spectral response) of the image sensor varies according to the color of light. For these reasons, a light source device capable of separately adjusting a light quantity of light of each color has been known (see US2012/0157774 (corresponding to Japanese Patent Unexamined Application Publication No. 2012-125395)). The light source device described is capable of adjusting the light quantity of each of the B, G, and R light included in the white light. The US2012/0157774 describes that the light quantity of the B light is preferably greater than that of the G light and the light quantity of the G light is preferably greater than that of the R light (that is, the B light>the G light>the R light).
Reflectance of the object, for example, mucosal tissue and the like of large intestine decreases as the wavelengths of the illumination light become shorter. However, the light reflected from the surface layer of the mucosal tissue is mostly the light of short wavelengths. Because the surface layer of the mucosal tissue includes the microstructure such as capillaries (capillary vessels), it is preferred that the light quantities among the light of the respective colors satisfy the relationship the B light>the G light>the R light in generating an image including the microstructure as described in the US2012/0157774. In this case, the relationship among the signal levels of the image signals from the image sensor is expressed as “the B pixel signals>the G pixel signals>the R pixel signals”. The signal level of the R pixel signals may be low.
The US2012/0157774 describes that a special image is generated from the B pixel signals and the G pixel signals. The special image eliminates the R pixel signals, so that there is little degradation in image quality due to the above-described relationship among the light quantities. Recently, however, attention has been focused on a color enhancement process for performing image processing on an image captured using the white light, to clarify a border between a normal site and a lesion. In a case where the color enhancement process is performed, it is preferred that the image quality of a red image is at substantially the same level as those of the blue and green images.